hard-coded buffer size can crash saving output for large models

[rheiland]

A user shared his model with ~16Kx16K 2D domain and 10 substrates and ~40K cells. It crashed shortly after the simulation started. The reason was tracked down to this hard-code buffer size: https://github.com/MathCancer/PhysiCell/blob/master/BioFVM/BioFVM_MultiCellDS.cpp#L567

We might attempt doing a calculation to determine the size needed and also add a try-catch to exit more gracefully.

He's a grad student at Colorado State who posted on our slack general channel. He'd built his model using the Studio. I helped him fix his cells .csv syntax from histological data. @drbergman made him aware of the BIWT option in the Studio ICs tab.